Population Floors and the Persistence of Chaos
in Ecological मोदेल्स
Graeme D. Ruxton
Division of Environmental 6 Evolutionary Biology, Graham Kerr Building,
University of Glasgow, Glasgow G12 8QQ, United Kingdom
and
Pejman Rohani
Department of Mathematics, University of Utah, Salt Lake City, Utah 84112, USA*
Received March 27, 1996
Chaotic dynamics have been observed in a wide range of population models. Here we
describe the effects of perturbing several of these models so as to introduce a non-zero mini-
mum population size. This perturbation generally reduces the likelihood of observing chaos, in
both discrete and continuous time models. The extent of this effect depends on whether chaos
is generated through period-doubling, quasiperiodicity, or intermittence. Chaos reached via
the quasiperiodic route is more robust against the perturbation than period-doubling chaos,
whilst the inclusion of a population floor in a model exhibiting intermittent chaos may increase
the frequency of population bursts although these become non-chaotic. ] 1998 Academic Press
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